The present invention relates to an excavation and compaction equipment for the construction of piles.
From the European patent EP 1726718 A1 it is known a tool designed for carrying out piles through compaction of the soil during the step of ascent with inversion of the direction of rotation.
The tool of this patent is comprises a shaft body, carried by the drilling rod, provided:                in the lower part with a plate provided with digging teeth and rotating with the drilling rod to which it is connected;        in the upper part with a screw tract for collecting the excavation material and        in its central portion, always provided with screw, with an element for the compaction of the removed soil during the drilling, and with a blocking device selectively re-closable depending on the excavation and compaction conditions.        
In the body it is provided a canalisation for the passage of the externally supplied concrete and which exits in correspondence with the digging teeth.
One of the main issues caused by the tool described in that patent is the instability of the hole after the compaction which creates collapses and inclusions of soil in the part of the casting. In this way, the quality of the pile is scarce and in some cases not suitable for the application.
Furthermore, the parts which lock the counter-rotating structure of the tool to the soil, in such a way as to create a relative angular rotation between the part put into rotation by the rotation head and the one which carries the plate, in some cases can be not enough for completing the closing, with consequent issues in the carrying out of the pile because the part of the casting is not separated from the one wherein the soil is compacted.
In the most general conditions, it has been noticed that the trend of the compacted hole is to get tightened (revealed by the fact that in some cases it is difficult to insert the cages in the hole) because the axially limited compacted zone and the high specific working pressures, make uncontrolled transfers of material happen through the interspace plate-hole, with consequent inclusions of the soil in the zone used for the casting.
On the other hand, in other cases, the storage of the material against the part which provides the compaction creates a successive storage of compacted soil layers on the tool which, in certain typologies of soil, can lead to make a pile with diameter higher than the nominal one. This causes extra consumptions of the casting which are economically unexpected.